1. Field of the Invention
The invention relates to a device for measuring acceleration by varying the resonance of an optical interferometer.
2. Description of the Related Art
Optical resonators which are tuned by varying the internal optical path length are well known. This type of optical resonator has been named after its inventors and is known as a Fabry-Perot etalon or interferometer. Such a interferometer consists of a pair of partially reflecting mirrors separated at a predetermined distance. That predetermined distance, and any material medium therein, defines the resonant wavelength or frequency. A theoretical description of the Fabry-Perot etalon can be found Optical Electronics, 3rd Edition, by Amnon Yariv, the disclosure of which is hereby incorporated herein by reference.
It is also known that a mass suspended by a spring will produce a linear displacement when the stress in the spring is well within the elastic region. This is particularly true with small displacements which are well below the 0.2% yield point of the spring material. Accelerometers are distinguished from each other by their means for suspending the proof mass (the mass to be accelerated), means for damping movement of the mass, and the type of sensors used for measuring displacement. Most of the time, little or no consideration is given to the accelerometer's proof mass distribution about the spring. This neglect results in measurement errors produced by orthogonal accelerations and vibration rectification errors produced by mass distributions subject to dynamic vibrating environments.
It is desirable to have an accelerometer which senses displacement using optical interference. It is further desirable to have an accelerometer with reduced orthogonal acceleration and vibration rectification errors.